The purpose of this project is to examine immunological events during taeniid metacestode infection. Particular emphasis is placed on interactions between parasite membranes, antibody, complement and both specific and nonspecific effector cells. Ultrastructural, pathological, and immunochemical techniques are used to explore the mechanisms involved in immunologic attack on the parasite, and the means whereby established parasites are able to retain control of membrane function and preserve membrane integrity in the face of immunologic reactions on the part of the host. Growth and development in normal and immune hosts will be studied in an effort to determine the factors which characterize host cell reactivity in infected tissues. The immunogenicity of well defined parasite products will be studied. Studies include the characterization of antigens, and the adjuvant effect of B. pertussis, and the site at which immune reactions occur in orally or parenterally immunized rats. The effects of parasite products on coagulation and on gastro-intestinal cell turnover will be determined. Lipid constituents of parasites have been established and the role of lipid intermediates in surface macromolecule synthesis will be studied. Taeniid cestode infections in man and animals consititue a serious zoonotic and economic problem throughout the world. Fundamental to the continuity of the life cycles of these parasites is the ability of the larval stages to survive for extended periods of time within the tissues of mammalian intermediate hosts. That they are able to do so in immunologically competent animals, which may show a marked and specific antibody-mediated immunity to superinfection, is a paradox challenging to our understanding of resistance mechanisms in infectious disease.